PLYMOUTH condemned the Sky Blues to their worst defeat of the season on a miserable day at Home Park.
Four first-half goals from Ashley Barnes, Jamie Mackie, Alan Judge and Marcel Seip did the damage, while Keiren Westwood and Aron Gunnarsson were both taken off with injuries.
Chris Coleman stuck with the team who drew at Crystal Palace on Tuesday night.
City's passing was superior in the opening ten minutes but they failed to force a real attack.
Plymouth then took control of the game and scored with their first attempt. Scott Dann fouled the advancing Mackie on the wing, which resulted a yellow card. The free-kick was turned towards goal by Gary Sawyer - only for Westwood to save - but the follow-up cross was headed in by Barnes.
City could have been level a minute later when Clinton Morrison was fed through, but he couldn't connect with the ball properly and Romain Larrieu saved well.
Plymouth came close to extending their lead when a through-ball towards Mackie almost gave him a clear shot at goal, but pressure from Ben Turner was enough to remove the danger.
However, the home side could not been contained for long. A high-ball into the box was challenged for by Mackie and, when Westwood couldn't collect, Mackie tapped the ball into the net.
City protested the decision - but two minutes later the match was beyond doubt when Guillaume Beuzelin lost the ball to Judge, who hit an excellent shot into the top corner.
After the goal, Gunnarsson was replaced by Kevin Thornton due to an injury.
Plymouth maintained their pressure and, after Barnes came close again, they notched a fourth. Paul Gallacher swung in a corner and Seip tapped the ball home from three-yards.
In the 42nd minute, Dan Fox hit a free-kick from 30-yards - but Larrieu turned the ball over the bar.
Beuzelin picked up a yellow card for a foul in the last meaningful incident of the half.
The opening 15 minutes of the second period were stop-start after three injuries.
First, Westwood was replaced by Andy Marshall with a facial injury. Then, referee Clive Oliver suffered a hamstring injury and was replaced by Paul Graham. Finally, play was stopped for several minutes when Judge received a blow to the head.
Play after the stoppages was disjointed and the pace of the game dropped.
City did have two half-chances but could not find the net.
First, a scramble in the Plymouth box eventually rolled in front of Morrison, but he could not hit the target from close range.
Fox then tested Larrieu with another free-kick from range. His strike curled towards the bottom corner but the French shot-stopper palmed the effort wide.
The Sky Blues nearly got a goal back with their last attack of the game - but Morrison's flicked header from a Fox free-kick went just wide.
After three minutes of added time, referee Graham finally called an end to City's worst defeat of the season.
Coventry (4-3-3) : Westwood (Marshall 50); Osbourne, Dann, Turner, Fox; Beuzelin, Doyle, Gunnarsson (Thornton 29); Eastwood, Simpson, Morrison. Subs: Ward, Hall, Cain
Plymouth (4-4-2): Larrieu; Gray, Barker, Seip, Sawyer; Judge (Clark 74), Duguid, Fletcher, Gallagher; Mackie (Douala 74), Barnes (Fallon 74). Subs: Saxton (GK), Timar
Ref: Clive Oliver (Northumberland) - replaced by Paul Graham, 52
